I have a reverse rotation Chrysler 318 in a marine application. I replaced the original block with a 1990 roller cam Dakota block. When it was recently rebuilt, the mechanic used a rope seal like the original design. It leaks like a sieve and the engine compartment is covered in oil. Not so good.

I would like to change to a neoprene seal, but I do not think a neoprene reverse rotation seal was ever used by the factory in 318's, so you can't get one today, as far as I know.

I would be ecstatic if someone would tell me I'm wrong and provide me with a manufacturer and a part number.

In the alternative, I'm wondering if the 318 shares its rear main seal design and/or dimensions with any other block (Mopar or otherwise) that did use a reverse rotation rear main seal. Like, were there any industrial 318's that were reverse rotation?

Also, can anybody provide me with the dimensions of the factory 318 seal? I do have a supplier (a boat guy) who knows a manufacturer who might be able to find a matching reverse rotation seal if I can supply the dimensions. He came pretty close to matching a reverse-rotation small-block Ford that way.

Of course I could go back with a rope seal, but the engine is out of the boat at the moment and I'd like to go with neoprene while I'm going to the trouble.

BTW, apparently the issue of rear main seals and standard v. reverse rotation is that there are hash marks on the neoprene seal that are oriented in a certain direction to direct the oil back into the crankcase. They would have to be oriented in the opposite direction for a reverse rotation crank. Apparently that's the only difference between the two seals.

And, no, I can't change over to standard rotation.

-Thomas